Broadband flexible wave guides

ABSTRACT

A flexible waveguide has an elongated hollow body having a noncircular cross section in which the ratio of the width of the wide side to the narrow side is less than 0.5. The body cross section includes an indentation extending along the longitudinal axis of the wave guide. The indentation is so shaped and the ratio of the width of the wave guide at the indented point to the width of the narrowest side is so small that interfering wave types do no occur.

United States Patent Schuttloffel etal. 14 1 Apr. 25, 1972 [54]BROADBAND FLEXIBLE WAVE 3,396,350 8/1968 Krank et a1. ..333/95 GUIDES3,444,487 5/1969 Krank et a1. ..333/95 A [72] Inventors: ErichSchuttloifel; Gerhard Schickle, both FOREIGN PATENTS OR APPLICATIONSBacknang Germany 1,462,731 11/1966 France ..138/118 [73] Assignee:Telefunken Patentverwertungsgesellschaft 425,104 9/1947 Italy m.b.H.,Ulm (Danube), Germany 1,025,473 3/1958 Germany .L ..333/95 A 1 Filedr p1969 OTHER PUBLICATIONS 1 1 PP N04 356,272 Harvey, A. F., MicrowaveEngineering" Academic Press,

1963, pp. 60-62 [30] Foreign Application Priority Data llgtadehn,Sprr-O-Gu1de, Ad In Mlcrowave Jr. 3- 1968, p. Sept. 21, 1968 Germany ..P17 90 171.2 Chen, T. S. Calculations of the Parameters of RidgeWaveguides, MTT- 5,No. 1, 1- 1957, pp. 12-17 [52] US. Cl. ..333/95 A,333/95 R, 138/172, Harvey, A. F., Microwave Engineering," AcademicPress,

l38/D1G. 11 1963, pp. 21-27 [51] lnt.Cl. ..H01p3/l4,F16111/14 [58] Fieldof Search ..72/368, 369; 138/ I I8, 172, Primary Examiner-Herman KarlSaalbach 138/177, DIG. 8, DIG. I I; 333/95, 95 A Assistant Examiner-Wm.H. Punter Attorney-Spencer & Kaye [56] References Cited ABSTRACT UNITEDSTATES PATENTS I .A flexible waveguide has an elongated hollow bodyhaving a 2,479,288 8/1949 Allen ..333/95 A nomcircular cross section inwhich the ratio f the width f 3105501 9/1965 Kuhn 333/3! X the wide sideto the narrow side is less than 0.5. The body 1923-163 4/1912 Money"mus/172 cross section includes an indentation extending along the lon-1,839,919 1/1932 Hall ..l38/l77 X gitudiha] a f the wave guide Theindentation is so Shaped 1,859,259 5/1932 Chamberlam et a1 ..l38/l77 Xand the ratio of the width of the wave guide at the indented 1,928,0099/1933 Dormer ..138/177 point to the width f the narrowest side i sosmall that inter- 2,406,838 9/1946 Kepler ..72/368 f i wave types do nooccuh 3,239,002 3/1966 Young .138/172 X 3,299,374 1/1967 Schickle et a1..333/95 A 4 Claims, 2 Drawing Figures O I 1 I. h 3

7) 3 d b B PATENTED R2 I9YZ 3,659,234

a c i zK //l 3 f 5/ /}i l l Inventors. Erich Schiifilffel GerhardSchickle BY a ATTORNE S.

BROADBAND FLEXIBLE WAVE GUIDES BACKGROUND OF THE INVENTION Thisinvention relates to wave guides, and more particularly to a wave guidewhich is provided with at least one indentation for preventing theformation of interfering waves.

Most wave guides with rectangular cross section used in commercialinstallations are of a standard type which has a ratio of narrow tobroad side width of 0.5. This ratio results in generally cleartransmission with relatively low attenuation in the transmission range.For special purposes, such as the transmission of very broad frequencybands this standard cross section may be deviated from.

Some rectangular wave guides are formed with one or two metal stripsextending along the longitudinal axis of the wave guide. These arecalled ridged wave guides and generally conduct a wider band width. Itis difficult to manufacture these in desired lengths, or to make themflexible.

Among the objects of the present invention is the provision of a waveguide which may be used for the transmission of a relatively wide bandwidth without producing an interfering second wave type (un wantedmode).

Other objects of the present invention include the provision of such awave guide which can be made to desired lengths, and which can be madeflexible.

SUMMARY OF THE INVENTION Briefly stated, these and other objects of theinvention are achieved by provision of a wave guide having a ratio ofnarrow side to broad side width of less than 0.5, and having anindentation formed so as to extend longitudinally along the wave guidebody. The ratio of the width of the wave guide cross section at theindentation to the wave guide narrow side is made sufficiently small,and the indentation is appropriately shaped so that the occurrence of aninterfering second wave type is prevented.

The wave guide may have two symmetrical indentations, may have planarwall portions in the area of the indentation, and may have a dielectricstrip mounted within it between the indentations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional viewthrough a wave guide formed according to one embodiment of theinvention.

FIG. 2 is a cross-sectionalview, similar to FIG. 1, of anotherembodiment ofthe present-invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, there isdisclosed a wave guide according to the present invention. It includes agenerally rectangular hollow body 7 having rounded corners. It has awide side A and a narrow side B. Two symmetrical indentations 5 and 6are formed which are extended toward each other and are integral withthe broad or wide sides of the wall 2 of the rectangular body 7. Thebody has a cross sectional profile which is constant along thelongitudinal axis of the body. The inner cross section of the body, asdefined by the inner periphery 1 of wall 2, has a width a along itsbroad side, a width b at the widest part of its narrow side, and a widthd between the indentations 5 and 6. Width d extends in the same generaldirection as the width b of the narrow side, but is less in dimensionthan the width b of the narrow side. The lines along which the greatestwidth b occurs are separated from each other by a distance 6.

A dielectric strip 3 is mounted within the hollow body between theindentations 5 and 6. The hollow body can be wound on a drum or twisted.When this is done, the dielectric 3 mounted within the hollow bodybetween the two indentations prevents contact between the opposite waveguide walls and limits the amount of deformation occurring in the areaof a bend.

Another embodiment of the invention is schematically represented in FIG.2. Corresponding parts of the structure of FIG. 2 have referencenumerals corresponding to the similar parts of FIG. 1. The portions 4 ofthe wave guide wall in the region of the center of the indentations areparallel to each other. In this case the wall 2 of the hollow body ismade with portions of greatest wall thickness e along the oppositenarrow sides, rather than in the region of the indentations as in theFIG. 1 embodiment. This prevents displacement of the cross section andbuckling when the wave guide is bent around a broad side a. Asillustrated, the inner and outer peripheries of the cross-sectionalprofile of the wave guide wall 2 are continuous smooth curves withoutabrupt changes in direction. The wave guide of either embodiment isconstructed as a seamless metal tube which is drawn to any desiredlength in a suitable machine. The wall thicknesses of the wave guidesare selected so that a prescribed radius of curvature can be maintainedwhen it is bent about a given radius of curvature or twisted through agiven radius of curvature.

The ratio of d/b is maintained at such a level and the indentationsare'of an appropriate shape so that no interfering wave types arise.

The arrangement according to the present invention permits an extremelywide band width to be transmitted and prevents undesired occurrences ofinterfering wave types. One particularly advantageous use for these waveguides is the transmission of linearly polarized I-I (TE) waves overantenna feeder lines which lead to a listener-receiver, i.e. a receiverwhich intended to receive as wide a frequency band as possible from theantenna. With this type of device the attenuation of the wave guide isof lesser significance.

In order to determine the wave conducting properties, a number of tubeshaving the following dimensions were constructed;

TABLE I Example I a 43.2 mm. b I 21.2 mm. d 20.9 mm. d/a 0.48 d/b 0.99b/a 0.49 Band Width Transmitted Without Interfering Side Waves even inbendings and twisted sections l0 Example 2 a 40.0 mm. b 13 mm. d l0.5mm. d/a 0.27 d/b 0.8 b/a 0.33 Band Width Transmitted Without InterferingSide Waves even in bendings and twisted sections l0 A number of tubes ofthe type of FIG. 2 were constructed. These were then bent about one oftheir broad sides and twisted through torsional angles until theybuckled. The results are set out below:

TABLE II A 45.3 mm. a 40 mm. B 21 mm. b 13 mm. c 25 mm. d 10.5 mm. Min.Radius of Curvature mm. Max. Torsional Angle about a guide length of onemeter Between the range of table I the attenuation of the wave guide isequal or better than that of standard type guides. If the ratio d/b ischoosen to be smaller, the attenuation increases but the transmittedband width also increases. It is theoretically possible to enlarge theindentations 5 and 6 until they nearly reach each other in order to geta band width as great as possible.

having a minimum narrow side width d between said indentations; saidindentations being so shaped and the ratio d/b being so small as toprovide a means for preventing the formation of interfering waves; andsaid cross-sectional profile of said wall of said tube having a maximumWe claim:

l. A twistable flexible wave guide of the type which can be wound on adrum and has a broad transmittable bandwidth comprising:

an elongated relatively thin-walled flexible seamless metal 5 tubehaving a constant noncircular cross-sectional profile along itslongitudinal axis with the wall of said tube having a thickness whichvaries along its cross-sectional profile;

thickness along the opposite narrow sides thereof and a minimumthickness in the area of said indentations, whereby displacement of theinner cross section of the the inner and outer peripheries of thecross-sectional profile of said wall of said tube being continuoussmooth curves without abrupt changes in direction; the inner crosssection of said tube, as defined by the inner periphery of the wall ofsaid tube, having a wide side of width a and a narrow side of width b atthe widest portion thereof with the ratio b/a being less than 0.5; saidwall of said tube being shaped so that said inner cross section has apair of symmetrical indentations which are opposite one another on thewide side thereof and which extend along the longitudinal axis of thetube, said inner cross section wave guide and buckling thereof isprevented when the wave guide is bent about the wide side thereof.

2. Thewave guide of claim 1 wherein the portions of the wall of saidhollow tube in the area of largest indentation are approximately planar.

3. The wave guide of claim 1 wherein said hollow tube is made ofaluminum.

4. The wave guide of claim 1 in which the tube is shaped fortransmission of linearly polarized H (TE) waves.

1. A twistable flexible wave guide of the type which can be wound on adrum and has a broad transmittable bandwidth comprising: an elongatedrelatively thin-walled flexible seamless metal tube having a constantnoncircular cross-sectional profile along its longitudinal axis with thewall of said tube having a thickness which varies along itscross-sectional profile; the inner and outer peripheries of thecross-sectional profile of said wall of said tube being continuoussmooth curves without abrupt changes in direction; the inner crosssection of said tube, as defined by the inner periphery of the wall ofsaid tube, having a wide side of width a and a narrow side of width b atthe widest portion thereof with the ratio b/a being less than 0.5; saidwall of said tube being shaped so that said inner cross section has apair of symmetrical indentations which are opposite one another on thewide side thereof and which extend along the longitudinal axis of thetube, said inner cross section having a minimum narrow side width dbetween said indentations; said indentations being so shaped and theratio d/b being so small as to provide a means for preventing theformation of interfering waves; and said cross-sectional profile of saidwall of said tube having a maximum thickness along the opposite narrowsides thereof and a minimum thickness in the area of said indentations,whereby displacement of the inner cross section of the wave guide andbuckling thereof is prevented when the wave guide is bent about the wideside thereof.
 2. The wave guide of claim 1 wherein the portions of thewall of said hollow tube in the area of largest indentation areapproximately planar.
 3. The wave guide of claim 1 wherein said hollowtube is made of aluminum.
 4. The wave guide of claim 1 in which the tubeis shaped for transmission of linearly polarized H10 (TE) waves.